Tetraheptylammonium capped magnetic nano Fe 3 O 4 was synthesized and used in the study of in vitro drug accumulation inside leukemia K562 cell lines. Confocal fluorescence microscopy methods were used to detect the fluorescent signal strength of doxorubicin in the absence and presence of nano Fe 3 O 4 . Atomic force microscopy (AFM) was used to characterize the surface structure of the leukemia cells. In addition, MTT assay was used to evaluate the safety and effectiveness of the presence of nano Fe 3 O 4 . Our results demonstrate the synergistic enhancement effect of the nano Fe 3 O 4 on respective drug uptake of doxorubicin for drug sensitive and drug resistant leukemia K562 cells. These observations indicate that the tetraheptylammonium-capped nano Fe 3 O 4 could efficiently enhance the relevant drug permeation into cancer cells through internalization/endocytosis processes and result in significantly enhanced doxorubicin uptake in respective leukemia K562 cells.